I don't want to get scammed by the electronic store

[flyingpig]

Homework Statement

A voltage - potential difference- is really just a measure of how badly electrons want to go from one terminal to the other. By connecting a wire, we create an E-field within that wire - the only path.

Now my problem is, I used to think a battery - a source of voltage - is source of energy that drives these electrons charges from one end of the terminal to the other. So what does having a higher volt battery mean? Isn't it more inefficient?

If I some light bulbs and it only need 7V, but if I insert a 8V will the bulb go brighter?

 

[cepheid]

Homework Statement

A voltage - potential difference- is really just a measure of how badly electrons want to go from one terminal to the other. By connecting a wire, we create an E-field within that wire - the only path.

Yeah, that seems reasonable.

Now my problem is, I used to think a battery - a source of voltage - is source of energy that drives these electrons charges from one end of the terminal to the other. So what does having a higher volt battery mean? Isn't it more inefficient?

Um, well I think you answered your question of what having a higher voltage means in your above statement of what potential difference is.

If I some light bulbs and it only need 7V, but if I insert a 8V will the bulb go brighter?

Yes, well as you well know, the bulb will get brighter, because it has a certain resistance, and if you put a higher voltage across that resistance, the current drawn will be larger, and the total power dissipated will be greater (leading to a brighter bulb). That is just Ohm's law.

Typically you choose your voltage based on the application. For instance, maybe you need a certain voltage to "turn on" an LED in a circuit. Or maybe you're using some sort of chips that only function with voltages in a certain range (this is determined by the type of digital logic used in those chips). There has been a move towards so called "low power" chips that do use lower voltages to reduce power consumption, and make it so that switching the signal on a line from "low" to "high" (in the digital logic sense) requires a lower overall voltage swing.

What could be the advantage of having a higher voltage? Well, if you are powering a device or load that has a fixed power consumption*, raising the voltage will mean lowering the current drawn. That will allow you to get away with smaller conductors saving on costs. If powering off batteries, it also means those batteries will last longer. This is also similar to the reason why they use really high voltage transmission lines to transmit electrical power. The power plant produces a fixed power, and increasing the voltage lowers the current, leading to fewer Ohmic (resistive) losses over the transmission lines.

*Obviously a light bulb/resistor is not an example of something that uses a fixed power

EDIT: I threw a bunch of random examples in this post to illustrate that there are any number of reasons why you'd pick a given voltage in a given situation.